Timing arrangements answering to the generic definition given hereinabove are known.
An installation for the identification and determination of the instant of passage of a plurality of moving objects at a predetermined point of their trajectory is described in the patent EP-B-0074330 (USA-4 551 725). This installation, particularly adapted for timing automobile races, comprises in particular an arrangement mounted on board each moving object, a fixed receiving antenna and means for processing identification signals broadcast by the transported arrangements. Furthermore, a transmitter is provided which serves on the one hand to trigger means for developing identification signals and which on the other hand serves as reference for these means which thus do not include their own time base.
The installation which has just been summarily described gives rise to the difficulty of being utilizable for a limited number of vehicles only Furthermore, the apparatus to be carried is relatively cumbersome which limits its employment to vehicles having a sufficiently large volume.
To overcome these difficulties, the installation described in the document FR-A-2 619 644 includes a plurality of main transmitters carried by the respective vehicles, each to detect and generate an electromagnetic wave modulated by a high frequency associated respectively with the vehicle under consideration, such electromagnetic wave being preferably in the infrared range. The installation further includes a principal receiver comprising a sensor based at a fixed station proximate a detection place and sensitive to the electromagnetic waves generated by the different main transmitters. The receiver further includes a plurality of modules, in number equal to the number of transmitters, each provided with discrimination means adapted to respectively isolate a specific high frequency component from the signal issued by the sensor and means adapted to detect the maximum amplitude of such component.
Aside from the fact that the recommended infrared wave may present transmission difficulties, the installation presents the difficulty of requiring the employment of as many different receivers as there are vehicles which overburdens and complicates considerably the receiver. Such receivers moreover call on old technologies, those in particular of the superheterodyne which as long known require as many local oscillators as there are frequencies under consideration in order to bring about the change of frequency. These techniques are burdensome and necessitate a large number of components.
This invention has as its purpose to avoid the difficulties described hereinabove in calling on a single receiver which is sensitive to the various broadcasts coming from the vehicles, such receiver exhibiting a relatively simple structure because of its employment of digital sampling techniques. Such techniques have never been proposed for timing sporting races.